2-bed RTOs are susceptible to vacuum spikes.  By definition, it is the nature of all RTOs to change the flow direction through the beds at regular intervals to exchange heat.  2-Bed RTOs must internally reverse the flow between the two beds when the flow direction is changed.  While most 2-Bed RTOs attempt to reverse the flow reversal as quickly as possible, there is still a period of approximately one second when both inlet and exhaust ports to each bed are open and the untreated process is able to bypass the RTO.  During this bypass period, the pressure drop of the beds is momentarily removed and the process fan which produces a constant differential pressure transfers the excess energy from the momentary loss of back pressure to the inlet ductwork in the form of a vacuum spike.  While it is often overlooked when selecting an RTO, the magnitude of the vacuum spike can be quite severe and wreak havoc on many processes such as web handling, semiconductor, etc.

TRITON™ RTOs differ with the availability of a 3^RD bed.   TRITON™ RTOs do not reverse the flow internally, rather the flow is rotated through the beds.  The rotation avoids opening the inlet and exhaust ports simultaneously.  Therefore, the process is never bypassed and thus no appreciable vacuum spikes are created.